1. Field of the Invention
This invention relates to a magnetic head and a method for the production thereof. More particularly, this invention relates to a magnetic head for use in a magnetic disk drive or a magnetic tape drive and a method for the production thereof.
2. Field of the Invention
The magnetic disk drive or the magnetic tape drive has come to be improved markedly in track density in consequence of the increase in the device's recording density and, therefore, is in need of a magnetic head which features a narrow core width and suffers only sparing recording obscurity. Particularly when the MR head (magnetoresistive head) which has been finding growing acceptance is to be used, since shared use of a magnetic layer of a large width destined to form a magnetic shield for the MR head as one of the two recording magnetic poles opposed to each other across a recording write gap layer is popular and also is liable to aggravate recording obscurity, it is preferred to adopt a magnetic head which suffers only sparing recording obscurity and enjoys a perfect off-track characteristic.
It is known that equalization of the upper and lower recording magnetic poles in width is effective in realizing such a magnetic head featuring a narrow core width and suffering only sparing recording obscurity as mentioned above. Various methods have been proposed for the production of magnetic heads of this description.
An example of trimming a magnetic pole from the air bearing surface (ABS), i.e. the face opposite a magnetic medium, side with a focused ion beam (FIB) will be cited. The magnetic head disclosed in JP-A-03-296,907, for example, is claimed to be a magnetic head of a perfect off-track characteristic which is obtained by trimming the upper and lower magnetic poles with the fib from the air bearing surface (abs) side of the magnetic head.
Specifically, after a slider 101 possessed of a rail face (air bearing surface (ABS)) 102 is formed as illustrated in FIG. 1A, the lateral part of an upper magnetic pole 104 of a magnetic head 103 formed on the slider 101 is trimmed by exposure to a focused ion beam and, at the same time, the upper layer part of a lower magnetic pole 105 is simultaneously trimmed to equalize the lower magnetic pole 105 and the upper electrode 104 in width as illustrated in FIGS. 1B and 1C.
Besides this method, the method which comprises forming the upper magnetic pole and subsequently trimming the lower magnetic pole as by ion milling with the upper magnetic pole itself as an etching mask during the course of a wafer process has been known. Since this method avoids adjusting the width of the upper magnetic pole by the trimming, the accuracy of the width of the upper magnetic pole depends on the accuracy of a plating pattern to be used for the formation of the upper magnetic pole.
The method which effects the trimming of the upper magnetic pole 104 and the lower magnetic pole 105 as illustrated in FIGS. 1A-1C, however, entails the following problems.
First, since the exposure to the focused ion beam is carried out after a given wafer has been cut into blocks and the rail face 102 has been formed on such a block, the handling of the substrate and the location of the focused ion beam are complicated. Further, this method is highly problematic in terms of reliability because depressions 106 formed in the rail face 102 as illustrated in FIG. 1C are fated to collect dust and lubricant therein when the rail face 102 contacts the face of the recording medium in the contact start and stop (CSS) area.
JP-A-03-296,907 (KOKAI) teaches to cope with this problem by filling the depressions with a nonmagnetic material. The work of filling the depressions itself is very difficult because the substrate on which the rail face is fabricated is no longer a wafer but a small block.
Further, the edges of the depressions which are formed by the focused ion beam are liable to form R's, approximately 0.1-0.2 .mu.m in size. This size of the R's does not deserve to be ignored when the core width approximates closely to 1 .mu.m.
Moreover, since the FIB electrically charges the rail face 102 being fabricated unless this face completely undergoes a treatment for electric neutralization, it inevitably breaks the MR element which is vulnerable to static electricity.
The method which consists in coping with this problem by subjecting the magnetic shield layer to ion milling with the upper magnetic pole as an etching mask during the course of wafer process has been known. Though this method allows easy handling of the substrate which has the unit size of a wafer, it is still at a disadvantage in inevitably etching parts other than the magnetic pole, suffering the redeposited film of the etched part to adhere to the lateral face of the magnetic pole, and rendering it difficult to improve the accuracy of core width.